Split muffins and cut into cubes. Alternate even layers of muffin cubes and ham in lightly greased 8-inch square baking dish. In medium bowl, beat together eggs, milk, mayonnaise, lemon peel and lemon juice until well blended. Pour evenly over muffin-ham mixture. Cover. Refrigerate several hours or overnight.
Uncover. Bake in preheated 350 degree F oven until golden brown and knife inserted near center comes out clean, about 50 to 60 minutes. Garnish with chives and lemon slices, if desired.